1. Technical Field
The present invention relates to a mold and a manufacturing method, and in particular, relates to a mold used when manufacturing a tube by extrusion molding and a manufacturing method of a tube using the same.
2. Related Art
There exist a fluid transfer tube in which a plurality of mutually independent flow paths are integrally formed by a resin material. In JP-B-58-041180, manufacturing of a tube for piping equipped with tube portions of various specifications by a series of processes including extrusion molding is described. Thereby, manufacturing processes can be reduced as compared with the case of manufacturing by processing and building up a given metal tube. Note that the tube for piping described therein includes the one having the strength by which inlet backpressure or the like can be distributed.
In JP-UM-A-6-000746, a structure in which a plurality of mutually parallel ink tubes are integrated by simultaneous molding. Thereby for example, an ink tube which enables to simultaneously supply a plurality of color materials can be supplied at low cast.
In JP-B-7-002362, forming an opening having a predetermined bore diameter in a molded product by molding while injecting gas into inside of the molded product in the manufacturing of a pipe material by extrusion molding is described. Thereby size accuracy of the molded product which cannot be fully controlled only by a shape of a mold can be corrected.
As described above, a multi line tube having a plurality of flow paths can be preferably used in various devices in which a plurality kinds of fluids are simultaneously treated. The multi line tube having continuous flow paths can be manufactured by extrusion molding using a mold equipped with a core which defines inner surface shapes of the flow paths and a die surrounding the outer side of the core with a space with respect to the core. A melt state or softened state material resin is injected into such a mold from one end of a resin flow path formed between the core and the die and a molded product is continuously extruded from an extrusion opening formed at the other end of the resin flow path. Accordingly, a long molded product can be continuously molded by continuously supplying a material resin.
Incidentally, a plurality of flow paths having the same size are basically arranged in the specification of the multi line tube as described above. Accordingly, a mold having a core and die having the same size in response to each line of the multi line tube is fabricated. However, when a multi line tube is actually manufactured by using such a mold, there is a case that inner diameters of the flow paths mutually formed in the lines are different. In addition, in a particular application, a multi line tube in which flow paths having different diameters are combined may exist. At any rate, a multi line tube having the same inner diameter is a basic, so that a technology for manufacturing a multi line tube in which flow paths mutually having the same inner diameter are combined has been required.